Field
The field relates to biodegradable wads associated with shotgun shells often used in and around aquatic environments.
Description of the Related Art
Shotguns are one of the most widely produced firearms worldwide. For example, the number of new shotguns manufactured in the United States was close to one million in 2011. Moreover, the annual production of shotgun shells is in the billions. Almost every shotgun shell that is fired discharges a wad (i.e., a “spent” wad) at a substantial distance from the sportsman. This distance prevents facile recovery, and the spent wad subsequently becomes pollution. Typically, and especially when lead shot is not used, the wad is composed of plastic that does not biodegrade, meaning the pollution is persistent in the environment.
The wads have multiple purposes in shotgun ammunition: (1) they separate the powder from the shot; (2) they expand to form a gas seal that retains the gas blast behind the shot as it travels down the barrel, efficiently maintaining velocity; (3) they provide protection to the barrel (particularly important when non-lead shot is used); (4) they can provide a cushioning effect to soften recoil; and (5) they can provide improved shot patterns and minimize distortion of the shot.
The effect of non-biodegradable plastic debris is significant. Abandoned shotgun wads can present safety, nuisance, and environmental problems on land and in freshwater, estuarine, and marine waters. When a waterfowl hunter fires a shotgun armed with a shell containing a non-biodegradable plastic wad, the wad is shot out of the gun and often flies into the adjoining water. The quantity of abandoned shotgun wads in the nation's waters is unknown; however, a shotgun wad is discharged with every shot fired, and many are abandoned. Target shooters (e.g., skeet, trap) often fire many shots in rapid succession, leaving a slew of plastic wads. Due to the range of shotguns and the locations in which they are fired, there is often no easy way for sportsmen to recover each spent shotgun wad.
Abandoned wads enter the food chain as non-biodegradable plastic debris. Plastic wads are reported as one of the most common debris items collected during beach cleanups (NOAA. 2012. Guidebook to community beach cleanups). The buoyancy of many plastics causes the debris to float; therefore, plastic wads that do not wash ashore tend to float on the water's surface. The floating wads can be mistaken for food by waterfowl and other marine species. For example, wads have been found in the stomach contents of ocean-foraging birds including the albatross (The Conservation Report. 2009). The consumption of plastic can lead to reduced fitness of aquatic species.
Abandoned wads also damage sensitive habitats. Over time, non-degradable plastic wads can break apart, causing massive amounts of non-degradable microplastics to enter the aquatic ecosystem. Currents can deposit the floating wads on distant river banks and coasts, thereby impacting all marine habitats, even habitats where hunting is prohibited. Furthermore, non-degradable plastic components can remain largely intact even after spending years afloat, before fracturing into smaller microplastics. The microplastics can adsorb organic toxins, and do not readily break down into compounds that can be assimilated into the natural carbon cycle.
Due in part to their low cost and versatility, production of plastics is likely to continue to increase. Worldwide commodity plastic production has increased by roughly 9% annually since 1950, with over 300 million tons produced annually in 2016. Approximately 60% of all the plastic ever made is accumulating in landfills and the natural environment (Geyer, R, et al., “Production, use, and fate of all plastics ever made”, Science Advances, 19 Jul. 2017, Vol. 3 (7): e1700782). It is likely that the increase in plastic production mirrors the increase in aquatic debris. Additionally, around half the global population resides within 100 kilometers of a coastline. With coastal populations increasing, the amount of aquatic and land-based plastic debris is likely to rise.